共两步

第一步 指定版本源
执行 curl -sL https://deb.nodesource.com/setup_6.x | sudo -E bash -
setup_5.x 需要安装的版本号，替换数字就行。

vagrant@ubuntu-xenial:~$ curl -sL https://deb.nodesource.com/setup_6.x | sudo -E bash -

// 出现这个就说明正在成功安装了！

## Installing the NodeSource Node.js v6.x repo...


## Populating apt-get cache...

+ apt-get update
Hit:1 http://mirrors.tuna.tsinghua.edu.cn/ubuntu xenial InRelease
Get:2 http://mirrors.tuna.tsinghua.edu.cn/ubuntu xenial-updates InRelease [95.7 kB]    
Get:3 http://mirrors.tuna.tsinghua.edu.cn/ubuntu xenial-backports InRelease [92.2 kB]  
Get:4 http://mirrors.tuna.tsinghua.edu.cn/ubuntu xenial-security InRelease [94.5 kB]
Hit:5 http://repo.mysql.com/apt/ubuntu xenial InRelease                         
Fetched 282 kB in 0s (615 kB/s)                    
Reading package lists... Done

## Confirming "xenial" is supported...

+ curl -sLf -o /dev/null 'https://deb.nodesource.com/node_6.x/dists/xenial/Release'

## Adding the NodeSource signing key to your keyring...

+ curl -s https://deb.nodesource.com/gpgkey/nodesource.gpg.key | apt-key add -
OK

## Creating apt sources list file for the NodeSource Node.js v6.x repo...

+ echo 'deb https://deb.nodesource.com/node_6.x xenial main' > /etc/apt/sources.list.d/nodesource.list
+ echo 'deb-src https://deb.nodesource.com/node_6.x xenial main' >> /etc/apt/sources.list.d/nodesource.list

## Running `apt-get update` for you...

+ apt-get update
Hit:1 http://mirrors.tuna.tsinghua.edu.cn/ubuntu xenial InRelease
Get:2 http://mirrors.tuna.tsinghua.edu.cn/ubuntu xenial-updates InRelease [95.7 kB]    
Get:3 http://mirrors.tuna.tsinghua.edu.cn/ubuntu xenial-backports InRelease [92.2 kB]  
Get:4 http://mirrors.tuna.tsinghua.edu.cn/ubuntu xenial-security InRelease [94.5 kB]   
Hit:5 http://repo.mysql.com/apt/ubuntu xenial InRelease                         
Get:6 https://deb.nodesource.com/node_6.x xenial InRelease [3,914 B]
Get:7 https://deb.nodesource.com/node_6.x xenial/main Sources [765 B]
Get:8 https://deb.nodesource.com/node_6.x xenial/main amd64 Packages [960 B]
Get:9 https://deb.nodesource.com/node_6.x xenial/main i386 Packages [959 B]
Fetched 289 kB in 5s (51.9 kB/s)
Reading package lists... Done

## Run `apt-get install nodejs` (as root) to install Node.js v6.x and npm

第二步
安装 nodejs，执行 apt-get install nodejs !

vagrant@ubuntu-xenial:~$ sudo apt-get install nodejs

Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following NEW packages will be installed:
  nodejs
0 upgraded, 1 newly installed, 0 to remove and 90 not upgraded.
Need to get 10.1 MB of archives.
After this operation, 50.7 MB of additional disk space will be used.
Get:1 https://deb.nodesource.com/node_6.x xenial/main amd64 nodejs amd64 6.9.1-1nodesource1~xenial1 [10.1 MB]
Fetched 10.1 MB in 1min 25s (119 kB/s)                                                 
Selecting previously unselected package nodejs.
(Reading database ... 60366 files and directories currently installed.)
Preparing to unpack .../nodejs_6.9.1-1nodesource1~xenial1_amd64.deb ...
Unpacking nodejs (6.9.1-1nodesource1~xenial1) ...
Processing triggers for man-db (2.7.5-1) ...
Setting up nodejs (6.9.1-1nodesource1~xenial1) ...
vagrant@ubuntu-xenial:~$ node -v
v6.9.1
vagrant@ubuntu-xenial:~$ npm -v
3.10.8